Field of the Invention
The present invention relates generally to security systems for doors which utilize electromagnetic locking, and more particularly to an improved electromagnetic coil assembly for use with an electromagnetic door locking mechanism, which electromagnetic coil assembly incorporates an improved housing construction allowing the electromagnetic coil assembly to be easily and conveniently installed in its operating position on the frame of the door utilizing the electromagnetic locking mechanism.
Security doors have evolved over the years from simple doors with heavy duty locks to sophisticated egress and access control devices. In bygone times, heavy duty chains and locks were the norm on security doors which were not generally used, or which were used to prevent theft or vandalism. However, fire codes have made such relatively simple door locking systems obsolete, at least in most developed countries. Emergency exit doors are required by law to be provided in all commercial buildings, and such doors must be operative in the event of a fire, earthquake, or other emergency.
These exit doors are typically mechanical in nature, and are provided with heavy horizontal push bars, which unlock the door upon actuation of the push bar. Such mechanical mechanisms are subject to tampering using simple mechanical tools such as pry bars, and do not deter access by even relatively unsophisticated criminals.
As might be expected, the art reflects a number of more sophisticated locking mechanisms. A series of such devices is found in U.S. Pat. No. 4,257,631, in U.S. Pat. No. 4,328,985, in U.S. Pat. No. 4,354,699, in U.S. Pat. No. 4,652,028, and in U.S. Pat. No. 4,720,128, all to Logan, Jr. or Logan, Jr. et al. The Logan, Jr. patents begin with the Logan, Jr. '631 patent, which describes a system activated by a push bar which, upon depression, moves a switch carried by the door to sound an alarm and start a timer delay. After the delay, the door is unlocked.
The Logan '985 patent teaches a hydraulic system for accomplishing the delay prior to unlocking the door, and the Logan '699 patent describes a retrofit locking device of the same type, but usable with any door latching system. Such hydraulic systems are relatively complex, and present a substantial maintenance problem over time.
The Logan et al. '028 patent and the Logan, Jr. et al. '128 patent both teach an electromagnet mounted on a door jamb, an armature on the door held by the electromagnet to retain the door in the closed position, and a switch used to indicate when the door is being opened or tampered with. The Logan, Jr. et al. '128 patent adds a set of contacts to confirm that the armature properly contacts the electromagnet. These electromagnetic systems represented a substantial improvement in the art of door locking devices.
U.S. Pat. No. 4,439,808, to Gillham, describes another system which also uses an armature on a door and an electromagnet on the door jamb. The armature has shoulders to retain the door in the closed position even if someone exerts enough pressure on the door to otherwise slide the armature off of the electromagnet. U.S. Pat. No. 4,439,808, to Gillham, is hereby incorporated herein by reference.
Two other patents are relevant, particularly since they are both assigned to the assignee of the present invention. Specifically, these patents are U.S. Pat. No. 4,609,910 and U.S. Pat. No. 5,000,497, both to Geringer et al. The Geringer et al. '910 patent teaches a system with an armature on a door, an electromagnet on a door jamb, and a switch used to tell when an attempt is made to open the door. The Geringer et al. '497 patent teaches a novel door-mounted armature and door jamb-mounted electromagnet. U.S. Pat. No. 4,609,910 and U.S. Pat. No. 5,000,497 are both hereby incorporated herein by reference.
While these references represent a substantial improvement in the state of the art to date, there are still several disadvantages and problems inherent in the design and construction of presently known electromagnet core assemblies. For example, more inexpensive electromagnet cores may use a solid iron core, which results in poorer electromagnet characteristics. It is thus the practice on all but the cheapest electromagnet cores to utilize a laminated iron core, with the laminations typically being held together in a potted assembly. While this is an acceptable solution, it is far from optimal and may result in non-uniform laminated cores.
Another significant problem with presently known electromagnet core assemblies is that they are typically placed in a box, which is then screwed to the frame of the door to be secured. Little thought has been placed in designing an optimal interface with the door frame. As a result, typical electromagnet core assemblies are both difficult to install, and highly subject to tampering.
It is accordingly a primary objective of the present invention that it provide an improved design and related method of assembly for a laminated electromagnet core. It is also an objective that the construction and design of the improved electromagnet core enhance the manufacturability of the laminated electromagnet core, while simultaneously resulting in an electromagnet core assembly which exhibits excellent electrical and magnetic core characteristics. In addition, it is also an objective that the improved design and related improved method of assembly are necessarily both simple to accomplish and highly repeatable, thereby making the resulting electromagnet cores consistent in both construction and performance.
With regard to the electromagnet core assembly itself, it is an objective of the present invention that the apparatus which contains the improved electromagnet core and the electromagnet coil winding be designed to exhibit ease of initial installation as a primary feature. In addition, it is a further objective that ease of replacement of the electromagnet core assembly be extremely simple and quick to accomplish, thereby making thee present invention easier to service than any other similar system. It is a further objective of the present invention that the improved electromagnet core assembly utilize modular assembly to further enhance its serviceability. Despite these advantages, it is essential that the improved electromagnet core assembly be tamper-resistant to at least as high a degree as the best of the previously known devices.
The electromagnet core assembly of the present invention must also be of a construction which is both durable and long lasting, and it should also require that essentially no maintenance be provided by the user. In order to enhance the market appeal of the apparatus of the electromagnet core assembly of the present invention, it should also be of inexpensive construction to thereby afford it the broadest possible market. Finally, it is also an objective that all of the aforesaid advantages and objectives of the electromagnet core assembly of the present invention be achieved without incurring any substantial relative disadvantage.